Description:DESCRIPTION:
Field of the invention:
[0001] The present disclosure generally relates to the technical field of hydrogen gas sensors and in specific, relates to a metal free-hydrogen gas sensor that is cost-effective, environmental friendly and feasible for mass production.
Background of the invention:
[0002] Energy plays a crucial role in the development of human society. Over the past years, the demand for energy has increased with the rapid expansion of automobiles and other industrial sectors, which resulted in a significant rise in fuel consumption and pollution. The severity of environmental pollution and the increasing consumption of non-renewable fuels have generated great interest in the development of clean energy technologies as an alternative to fossil fuels.
[0003] At present, hydrogen gas is growing rapidly as a potential next-generation alternative fuel. Hydrogen is a clean source of renewable energy with high energy density. Therefore, hydrogen has the potential to be the future source of fuel with wide applications in aircraft, chemical processes, fuel cells, nuclear, medical, petrochemical, transportation, coal mines, thermal power stations, etc. However, a common risk associated with the use of hydrogen is its hazardous flammable and explosive properties under mild conditions.
[0004] In case of leakage, hydrogen is difficult to detect or sense through human sensory organs, as hydrogen is colorless and odorless in nature. Hydrogen gas is nontoxic in nature, but hydrogen can be explosive if its concentration reaches more than 4% in the air. Therefore, it is essential to strictly manage and supervise hydrogen gas in all of the technical fields that use hydrogen fuel energy. A technology for commercializing hydrogen fuel energy may be implemented with a highly sensitive method for detecting hydrogen that detects hydrogen gas leakage rapidly and accurately.
[0005] There are multiple technologies and devices used for sensing hydrogen that includes electrical sensors, chemical sensors chemochromic sensors, and metal based sensors thereof. The existing electrical hydrogen sensing devices are expensive, bulky, and complicated as they need additional components and an additional electric circuit in a detection region. Further, chemical hydrogen detecting sensors are capable for long-distance detection, and can be used multiple times. However, the sensitivity of these sensors towards hydrogen detection is very less.
[0006] In existing technology, a sensing device comprises hydrated or non-hydrated transition metal oxides and a shell includes a transition metal catalyst. The sensing device obtains response time of 10 minutes and a recovery time of 180 seconds. However, the cost, the recovery time and response time of the sensing device are high. Here, the sensor is fabricated with metal that attains high cost for purchase and the time taken for recovery and response is much high.
[0007] In general, the conventional hydrogen gas sensors, which are used to detect hydrogen, have a high manufacturing cost. The fabrication of these hydrogen gas sensors is complicated, and their design necessitates a high level of expertise. At present, the conventional hydrogen gas sensors as metal-based. Palladium (Pd) and Platinum (Pt) are the most popular metals used for hydrogen detection. The palladium-based hydrogen gas sensors are the most common and efficient.
[0008] However, palladium-based hydrogen gas sensors are very expensive. Further, only skilled people can synthesize and manufacture these palladium-based hydrogen gas sensors. The semiconducting metal oxides (SMO) based sensors are very good for the detection of hydrogen gas. However, the SMO based sensors require a very high operating temperature. Further, the SMO based sensors are not suitable for the detection of low-level hydrogen gas and has low response and recovery. Further, the metal-based hydrogen gas sensors are not eco-friendly.
[0009] In conventional methods, traditional detection methods are usually complicated and the testing instruments are expensive. The sensing devices are expensive due to metal fabrication and obtain high response time and high recovery time. However, traditional detection methods are usually complicated and the testing instruments are expensive.
[0010] Therefore, there is a need for a cost-effective and metal free- hydrogen gas sensor that is simple to design, eco-friendly and feasible for mass production. There is a need for a sensing device that does not require any precious metal doping. There is a need for a PVA based hydrogen sensor that is efficient, cost-effective and easily available.
Objectives of the invention:
[0011] The primary objective of the invention is to provide a cost effective hydrogen gas sensor that is simple, environmental friendly and feasible for mass production.
[0012] The other objective of the invention is to provide a metal-free hydrogen gas sensor that is eco-friendly and do not involve usage and emission of toxic chemicals during its fabrication.
[0013] The other objective of the invention is to provide portable hydrogen gas sensors that are designed with PVA thin films.
[0014] The other objective of the invention is to provide hydrogen sensors that are feasible for mass production.
[0015] Yet another objective of the invention is to provide a hydrogen sensor that does not require any precious metal doping.
[0016] The other objective of the invention is to provide a polyvinyl based hydrogen gas sensor that is easily fabricated.
[0017] Further objective of the invention is to provide a hydrogen gas sensor with good stability and precision.
Summary of the invention:
[0018] The present disclosure proposes a metal-free hydrogen sensor and method of fabrication thereof. The following presents a simplified summary in order to provide a basic understanding of some aspects of the claimed subject matter. This summary is not an extensive overview. It is not intended to identify key/critical elements or to delineate the scope of the claimed subject matter. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.
[0019] In order to overcome the above deficiencies of the prior art, the present disclosure is to solve the technical problem to provide a metal-free hydrogen gas sensor that is cost-effective, environmental friendly and feasible for mass production.
[0020] According to an aspect, the invention provides a metal-free hydrogen sensor. The metal-free hydrogen sensor comprises an interdigitated electrode and at least one thin film. The interdigitated electrode material includes either a gold electrode or other similar electrodes. The thin film is made of a pure form of vinyl alcohol positioned on the interdigitated electrode to detect hydrogen. In specific, the vinyl alcohol includes either polyvinyl alcohol or other vinyl alcohols thereof.
[0021] The metal-free hydrogen sensor operates at an optimum temperature of around 200°C for sensing hydrogen with a response percentage of 30%. The metal-free hydrogen sensor exhibits a response time and recovery time of 15.80 seconds and 22.32 seconds respectively along with good stability and repeatability. In specific, the metal-free hydrogen sensor is a resistive type sensor that detects hydrogen based on adsorption.
[0022] According to another aspect, the invention provides a method for fabricating a metal-free hydrogen sensor. At first, the vinyl alcohol solution of 2% is poured into a micropipette. Next, the vinyl alcohol solution is drop casted on an interdigitated gold electrode (IDE). Finally, the metal-free hydrogen sensor is obtained by slow annealing the drop casted vinyl alcohol solution on the interdigitated gold electrode (IDE). In specific, the slow annealing provides a soft thin film of the vinyl alcohol solution on the interdigitated gold electrode (IDE).
[0023] Further, objects and advantages of the present invention will be apparent from a study of the following portion of the specification, the claims, and the attached drawings.
Detailed description of drawings:
[0024] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention, and, together with the description, explain the principles of the invention.
[0025] FIG. 1 illustrates an exemplary metal-free hydrogen sensor in accordance to an exemplary embodiment of the invention.
[0026] FIG. 2 illustrates an exemplary method for fabricating a metal-free hydrogen sensor in accordance to an exemplary embodiment of the invention.
[0027] FIG. 3 illustrates an exemplary graphical representation of the performance of a metal-free hydrogen sensor with respect to resistance and time in accordance to an exemplary embodiment of the invention.
[0028] FIG. 4 depicts an exemplary graphical representation of the response and recovery time of metal-free hydrogen sensors when exposed to hydrogen gas in accordance to an exemplary embodiment of the invention.
[0029] FIG. 5 depicts a graphical representation of the response and recovery time of metal-free hydrogen sensors when exposed to hydrogen gas for various concentrations in accordance to an exemplary embodiment of the invention.
Detailed invention disclosure:
[0030] Various embodiments of the present invention will be described in reference to the accompanying drawings. Wherever possible, same or similar reference numerals are used in the drawings and the description to refer to the same or like parts or steps.
[0031] The present disclosure has been made with a view towards solving the problem with the prior art described above, and it is an object of the present invention to provide metal-free-hydrogen gas sensor that is cost-effective, environmental friendly and feasible for mass production.
[0032] According to an exemplary embodiment of the invention, FIG. 1 refers to a metal-free hydrogen sensor 100. The metal-free hydrogen sensor comprises an interdigitated electrode 104 and a thin film 102. The interdigitated electrode 104 material includes either a gold electrode or other similar electrodes. The thin film 102 is made of a pure form of vinyl alcohol positioned on the interdigitated electrode 104 to detect hydrogen. In specific, the vinyl alcohol includes either polyvinyl alcohol or other vinyl alcohols thereof.
[0033] The metal-free hydrogen sensor 100 operates at an optimum temperature of around 200°C for sensing hydrogen with a response percentage of 30%. The metal-free hydrogen sensor 100 exhibits a response time and recovery time of 15.80 seconds and 22.32 seconds respectively along with good stability and repeatability. In specific, the metal-free hydrogen sensor 100 is a resistive type sensor that detects hydrogen based on adsorption.
[0034] The interdigitated electrode (IDE) 104 with the PVA film is placed on a heating chuck and probe contacts (tips) are gently placed on electrode contact pads to establish ohmic contacts. The material is slowly annealed to 200°C under Nitrogen flow and was stabilized. On exposure to hydrogen gas, the resistance of the metal-free hydrogen sensor gradually decreases and observes which corresponds to the response of material towards hydrogen gas.
[0035] In specific, hydrogen is a reducing gas. Hydrogen gas interacts with the polyvinyl alcohol in its dehydrated state provides electrons to it. These electrons increase the conductivity of the hydrogen sensor and thereby decrease its resistance which is measured by the source meter. However, this response is reversible and when the hydrogen gas is turned off the hydrogen quickly desorbs from the surface bringing the conductivity of PVA film back to its initial state.
[0036] According to another embodiment of the invention, FIG. 2 refers to a method 200 for fabricating a metal-free hydrogen sensor. At step 202, a 2% vinyl alcohol solution is poured into a micropipette. At step 204, the vinyl alcohol solution is drop casted on an interdigitated gold electrode (IDE). At step 206, the metal-free hydrogen sensor is obtained by slow annealing the drop casted vinyl alcohol solution on the interdigitated gold electrode (IDE). In specific, the slow annealing provides a soft thin film of the vinyl alcohol solution on the interdigitated gold electrode (IDE).
[0037] According to another embodiment of the invention, FIG. 3 refers to the performance of the metal-free hydrogen gas sensor with respect to resistance and time. When the hydrogen gas is detected by polyvinyl alcohol film then the electrons in the thin film are increased by hydrogen gas detection and thereby reducing the resistivity of the hydrogen gas sensor.
[0038] FIG. 3 depicts the graphical representation of the hydrogen sensor when affected by hydrogen gas. The horizontal axis represents time and the vertical axis represents resistance. Initially, the resistance of the hydrogen sensor is constant. When the hydrogen gas is switched ON, then the sensor detects the hydrogen gas and drastically reduces its resistivity. Later, when the hydrogen gas is switched OFF, then the sensor regains its resistivity.
[0039] According to another embodiment of the invention, FIG. 4 depicts the graphical representation of the response time and recovery time of metal-free hydrogen sensor when exposed to hydrogen gas. In specific, the horizontal axis represents time in seconds and the vertical axis represents the resistance in ohms.
[0040] According to another embodiment of the invention, FIG. 5 depicts the graphical representation of the response time and recovery time of metal-free hydrogen sensor when exposed to hydrogen gas of various concentrations. In specific, the horizontal axis represents time in seconds and the vertical axis represents the resistance in ohms.
[0041] For instance, table 1 depicts the study of the response percentage of polyvinyl alcohol (PVA) at different temperatures and annealing times.
[0042] Table 1:
S.No. Temperature °C Annealing time at 200°C
At 15 min
Response % Annealing time at 200°C
At 30 min
Response % Annealing time at 200°C
At 1 Hour
Response %
1. 200 °C 26.5 % 30.0 % 20.0%
2. 150 °C 23.0 % 25.0 % 12.2 %

[0043] Table 1 illustrates the annealing time and response for 200°C and 150°C. The highest response percentage obtained at 30 minutes of annealing time is 30%. The least response percentage is obtained at 60 minutes of annealing time is 12.2%
[0044] For instance, table 2 depicts the study of the response time and recovery time of the metal-free hydrogen sensor at different concentrations of hydrogen gas.
[0045] Table 2:
S.No. H2 + N2
(sccm)
Conc. of H2 (ppm) % Response
1V Response
Time (sec) Recovery
Time(sec)
1. 500 10000 32.26 15.80 22.32
2. 400 + 100 8000 25.21 14.30 23.22
3. 300 + 200 6000 17.17 11.86 18.81
4. 200 + 300 4000 11.86 9.33 19.46
5. 100 + 400 2000 6.13 8.27 18.81
6. 50 + 450 1000 2.00 7.41 16.33

[0046] Table 2 illustrates the response time and recovery time at different concentrations. By taking different combinations of the hydrogen gas with different concentrations the response time and recovery time varies from each other. The highest response percentage of hydrogen and nitrogen gas is 32.26% for (500+0) standard cubic centimetres per minute (sccm) concentrations and the least is 2% for (50+450) standard cubic centimetres per minute (sccm) concentrations.
[0047] The highest response time and recovery time obtained for (500+0) standard cubic centimetres per minute (sccm) concentrations are 15.80 seconds and 22.32 seconds. The least response time and recovery time obtained for (50+450) standard cubic centimetres per minute (sccm) concentrations are 7.41 seconds and 16.33 seconds.
[0048] Numerous advantages of the present disclosure may be apparent from the discussion above. In accordance with the present disclosure, a metal-free hydrogen sensor is disclosed. The proposed cost-effective hydrogen gas sensor is simple, environment friendly and feasible for mass production. The proposed hydrogen sensor does not require any precious metal doping. The proposed polyvinyl based hydrogen gas sensor is easily fabricated and provides good stability and precision.
[0049] The proposed metal-free hydrogen sensor is a flexible and portable hydrogen sensor. The proposed hydrogen sensor may be prepared with various alcohol solutions to obtain better response and recovery time. The proposed hydrogen sensor may be prepared using various types of electrodes for better performance. The proposed hydrogen sensor further uses various types of methods such as physical vapour deposition (PVD) and chemical vapour deposition (CVD) thereof for fabricating portable and flexible metal-free hydrogen sensor.
[0050] It will readily be apparent that numerous modifications and alterations can be made to the processes described in the foregoing examples without departing from the principles underlying the invention, and all such modifications and alterations are intended to be embraced by this application. , Claims:CLAIMS:
We Claim:
1. A metal-free hydrogen sensor, comprising:
an interdigitated electrode; and
at least one thin film made of pure form of a vinyl alcohol positioned on said interdigitated electrode configured to detect hydrogen,
whereby said hydrogen sensor is a low-cost metal free hydrogen sensor that is feasible for mass production.
2. The metal-free hydrogen sensor as claimed in claim 1, wherein said interdigitated electrode material includes either a gold electrode or other similar electrodes.
3. The metal-free hydrogen sensor as claimed in claim 1, wherein said metal-free hydrogen sensor operates at an optimum temperature of around 200°C for sensing hydrogen with a response percentage of 30%.
4. The metal-free hydrogen sensor as claimed in claim 1, wherein said metal-free hydrogen sensor exhibits response time and recovery time of 15.80 seconds and 22.32 seconds respectively along with good stability and repeatability.
5. The metal-free hydrogen sensor as claimed in claim 1, wherein said vinyl alchohol includes either polyvinyl alcohol or other vinyl alcohols thereof.
6. The metal-free hydrogen sensor as claimed in claim 1, wherein said metal-free hydrogen sensor is a resistive type sensor.
7. The metal-free hydrogen sensor as claimed in claim 1, wherein said metal-free hydrogen sensor detects hydrogen based on adsorption.
8. A method for fabricating a metal-free hydrogen sensor, comprising:
pouring 2% vinyl alcohol solution into a micropipette;
drop casting said vinyl alcohol solution on an interdigitated gold electrode (IDE), and
obtaining a metal-free hydrogen sensor by slow annealing said drop casted vinyl alcohol solution on said interdigitated gold electrode (IDE).
9. The method for fabricating a metal-free hydrogen sensor as claimed in claim 8, wherein said slow annealing provides a soft thin film of said vinyl alcohol solution on said interdigitated gold electrode (IDE).